This invention relates to methods and apparatus for handling, threading, and testing joints of tubular products, and more particularly relates to improved systems, methods and apparatus for handling, threading, and testing links of pipe, tubing, and casing commonly employed in the petroleum production industry.
Joints of tubing, pipe, and casing having long been utilized in the petroleum producton industry for recovering petroleum substances from underground formations. The requirements for such products, and particularly for the threads, may be different from the requirements for threaded tubular products in general. For instance, casing and tubing used in the petroleum industry is often fabricated with a large, internally threaded box portion at one end of the pipe, and a specially designed pin portion thread on the other end of the pipe. Alternatively, pin portions may be formed on both ends of the pipe, and a seperate coupling may be threaded on one end to function in a manner similar to the box portion. After the box portion has been formed and the threads cut into the pipe, a oil well customer typically requires that the internal diameter of each joint of pipe be checked, and that the pipe be fluid tested at a predetermined pressure.
The equipment for threading and pressure testing pipe, including pipe handling equipment for transporting pipe to various pieces of equipment, has been commercially available and is utilized by those generally engaged in threading pipe for the petroleum industry. Conventional equipment, however, has several drawbacks which limit its productivity and acceptance within the pipe threading industry.
It may be desirable that pipe threading equipment be easily moved to new locations, although much of the prior art equipment is not suited for such purposes. The petroleum industry may prefer pipe threading facilities near the particular location where drilling operations are most active, and it is therefore advantageous that such equipment be adapted to be periodically moved. Typically, conventional pipe handling equipment does not position each segment of pipe at a common elevation line at the stage prior to the machining or testing operation. Since elevation lines vary with different equipment, various machining or testing equipment cannot be added or deleted from the overall assembly without altering the pipe handling equipment. This substantially decreases the flexibility desired to periodically adjust the threading line to meet changing needs.
Some of the prior art pipe handling equipment bent or damaged the pipe, or transported the pipe to one or more threading or testing machines in a manner that had a tendency to damage the machines. Other prior art handling equipment does not have the ability of supporting a rotating pipe, so that the threading operation necessarily has to be accomplished on a stationary string of pipe. Even the handling equipment which is able to support a rotating length of pipe frequently allows unwanted vibration in the rotating pipe, so that the threading operation cannot be performed at desired pipe rotation speeds. Vibration in the rotating pipe also contributes to a low quality threading operation, so that the pipe may be rejected after the threading operation.
As previously noted, it is common for those engaged in pipe threading operations to form an expanded box portion at one end of the pipe. This box portion may be produced by cold-forming an end portion of the pipe in a radially outward direction, thereafter reforming the tip portion inwardly to approximately its original state, and finally forming internal threads on the tip portion of the box. The box portion may also be formed by radially expanding an end portion of the pipe, and thereafter internally threading the expanded portion. A pin portion may be formed on the other end of the pipe (or on both ends if a coupling is utilized instead of a box portion) by inwardly contracting the end of the pipe.
Equipment typically used to form the expanded portion of the box and reform the tip portion inwardly suffers from drawbacks associated with (a) misalignment of the box with the axis of the pipe, (b) uneven deformation of the sidewalls of the box, and (c) misalignment of the expanded sidewalls of the box and the reformed tip of the box. Also, the power sources for such cold-forming and reforming operations are expensive and operate in a time consuming manner.
The prior art is also seriously burdened with problems associated with the fluid test station which may be included in the overall pipe threading line. Powered equipment for threadedly engaging the end of the pipe and injecting fluid into the pipe offers a substantial increase in productivity compared to manual techniques, but is also capable of galling or otherwise damaging the threads of the pipe, thereby substantially destroying the value of the threaded pipe. Misalignment of the head of the test equipment and the threaded end of the pipe may result in damaged pipe, damaged test equipment, and down-time for the overall threading assembly.
Accordingly, there is a need for a pipe threading system, method, and apparatus which will perform the various operations associated with threading pipe in an efficient manner. Preferably, such a system will not only be capable of threading joints of pipe, but may also have the capability of forming box ends and pin ends on drill pipe, coating ends of pipe with a protective fluid, checking the internal diameter and straightness of the threaded pipe, fluid pressure testing the pipe, and handling the pipe in a safe and efficient manner with the various machines performing these or similar operations. Further, it is desirable that such a system be capable of threading and checking pipe at a rapid rate, and performing such operations with a minimum number of personnel.
The disadvantages of the prior art are overcome with the present invention. Novel methods and apparatus are hereinafter provided for threading, testing, and handling tubing, casing, and pipe utilized in the petroleum industry.